1. Field of the Invention
The invention proceeds from a component comprising a body composed of an alloy based on a .gamma.-titanium aluminide, a steel body and a connecting piece composed of a nickel-base alloy, by means of which connecting piece the .gamma.-titanium aluminide body and the steel body are rigidly joined together, the joint between the .gamma.-titanium aluminide body and the connecting piece being produced by friction welding. The invention also relates to a process for producing said component.
2. Discussion of Background
A component of the type mentioned at the outset and formed as rotor of a turbocharger and a process for producing said rotor have already been described by Y. Nishiyama et al., "Development of Titanium Aluminide Turbocharger Rotors", High Temperature Aluminides and Intermetallics, edited by S. H. Whang et al., The Minerals, Metals & Materials Society, 1990. The predisclosed rotor comprises a turbine wheel composed of a .gamma.-titanium aluminide and joined to a steel shaft by friction welding by means of a connecting piece composed of a nickel-based alloy having a nickel content of over 70 percent by weight. Such a rotor is notable for a shear strength which is determined by the .gamma.-titanium aluminide since the nickel-based alloy acts as a buffer and brittle phases which occur in the direct friction welding of .gamma.-titanium aluminide and steel are avoided as a result of the formation of a continuous diffusion layer at the joint between the .gamma.-titanium aluminide body and the connecting piece. High-alloy nickel-based alloys have a melting range situated at comparatively high temperatures. To activate the diffusion processes occurring during friction welding, a comparatively high energy is needed in the case of this alloy.